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.Dd March 30, 2020
.Dt GETFSSTAT 2
.Os
.Sh NAME
.Nm getfsstat
.Nd get list of all mounted file systems
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/param.h
.In sys/ucred.h
.In sys/mount.h
.Ft int
.Fn getfsstat "struct statfs *buf" "long bufsize" "int mode"
.Sh DESCRIPTION
The
.Fn getfsstat
system call
returns information about all mounted file systems.
The
.Fa buf
argument
is a pointer to
.Vt statfs
structures, as described in
.Xr statfs 2 .
.Pp
Fields that are undefined for a particular file system are set to -1.
The buffer is filled with an array of
.Fa statfs
structures, one for each mounted file system
up to the byte count specified by
.Fa bufsize .
Note, the
.Fa bufsize
argument is the number of bytes that
.Fa buf
can hold, not the count of statfs structures it will hold.
.Pp
If
.Fa buf
is given as NULL,
.Fn getfsstat
returns just the number of mounted file systems.
.Pp
Normally
.Fa mode
should be specified as
.Dv MNT_WAIT .
If
.Fa mode
is set to
.Dv MNT_NOWAIT ,
.Fn getfsstat
will return the information it has available without requesting
an update from each file system.
Thus, some of the information will be out of date, but
.Fn getfsstat
will not block waiting for information from a file system that is
unable to respond.
It will also skip any file system that is in the process of being
unmounted, even if the unmount would eventually fail.
.Sh RETURN VALUES
Upon successful completion, the number of
.Fa statfs
structures is returned.
Otherwise, -1 is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn getfsstat
system call
fails if one or more of the following are true:
.Bl -tag -width Er
.It Bq Er EFAULT
The
.Fa buf
argument
points to an invalid address.
.It Bq Er EINVAL
.Fa mode
is set to a value other than
.Dv MNT_WAIT
or
.Dv MNT_NOWAIT .
.It Bq Er EIO
An
.Tn I/O
error occurred while reading from or writing to the file system.
.It Bq Er EINTEGRITY
Corrupted data was detected while reading from the file system.
.El
.Sh SEE ALSO
.Xr statfs 2 ,
.Xr fstab 5 ,
.Xr mount 8
.Sh HISTORY
The
.Fn getfsstat
system call first appeared in
.Bx 4.4 .
